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I run an ICP-OES. I am looking for a maximum of 3.0% Mo in my sample. What PPM dilution should I use for my Standard? (500ml)

Question asked by P J on Nov 1, 2016

I just started a new job running an ICP-OES.  I am having trouble with my results for MO and the calculations for dilution.

 

I had previously calibrated with a purchased 500ml bottle of Mo standard at 100PPM.  We have an in-house base material that is dissolved as a check standard.  Up to this point, it always came in around 0.53% to 0.56%.

      A new lot of Mo standard was opened and all subsequent results dropped to 0.46% to 0.50%.  I dissolved a NIST iron chip standard with 4390PPM Mo. Diluted to 500ml brings it to 8.78%.  I created a method and calibrated with the NIST standard  and all my results were good.

 

1.)  Is the 100PPM vs. the 8.78PPM the reason for this?

2.) HOW do I calculate the PPM needed for 3.0% max. Mo.

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